Sciencemadness Discussion Board

Reusing instant cold packs > Development of green air conditioner

Pyro_cat - 23-7-2019 at 07:17


I should have done the experiment before posting but why wouldn't the endothermic reaction happen again if I simply dried out the nitrate salts and dissolved them in water again? I can't think of any reason.


"Four Instant Ice Packs provide you with the same chilling power as 10-20 pounds of ice." https://icemakergeeks.com/do-instant-ice-packs-work-an-item-...

If the above is true then a few hundred instant cold packs are equivalent to a one ton air conditioner.

Thinking how could one design a closed loop air conditioning system that uses solar energy to evaporate the water from the material, re condense the water then add it to the material again and repeat endothermic reaction .

This seems too easy, I am missing something.

[Edited on 23-7-2019 by Pyro_cat]

Metacelsus - 23-7-2019 at 08:52

Your idea is very similar to an absorption refrigerator. See here: https://en.wikipedia.org/wiki/Absorption_refrigerator#Simple...

Edit: And yes, it would work, although it's not the most efficient refrigeration method.

[Edited on 2019-7-23 by Metacelsus]

mayko - 23-7-2019 at 09:03

Sodium sulfate is used as a thermal storage medium in a similar manner:

https://en.wikipedia.org/wiki/Sodium_sulfate#Thermal_storage

WGTR - 23-7-2019 at 12:08

Pyro, this sounds like the kind of project that you would like:

https://www.youtube.com/watch?v=R_g4nT4a28U

DavidJR - 23-7-2019 at 12:11

Quote: Originally posted by WGTR  
Pyro, this sounds like the kind of project that you would like:

https://www.youtube.com/watch?v=R_g4nT4a28U


Here's a slightly different idea: https://www.youtube.com/watch?v=lfmrvxB154w

streety - 24-7-2019 at 17:02

This may also be of interest: https://www.youtube.com/watch?v=uJ_NpWnCXzM

I moved from an area where residential AC is the exception to an area where it is considered essential a few years ago. It does seem like there are a couple of major oddities in how AC is typically used:

1) AC is used when it is least efficient.

AC efficiency decreases as the temperature difference increases. Despite this it is generally used based on demand during the hottest time of the day. I suspect if used during the night to chill a large cold store which is then used to cool the living space during the day it would be a lot more efficient.

2) Reliance on electricity

It's usually sunny when AC is needed. As mentioned by Metacelsus and the Tech Ingredients video these alternative methods are usually less efficient but they can use cheaper heat sources such as hot water from a solar panel.

A major advantage of the current AC implementations is they can be used anywhere. A large cold store or solar panel will not work everywhere but there are plenty of places where they will.

WGTR - 24-7-2019 at 19:29

For those who are interested in staying cool, dew point is actually more important than regular dry-bulb temperature. One thing that I have never seen pointed out anywhere, is that it is easier to obtain a given dew point by removing latent heat rather than sensible heat in a typical house. This is because moisture ingress can be stopped effectively with just a thin sheet of plastic, whereas insulation is usually as thick as possible to stop "heat" ingress.

Modern construction practices in the U.S, are such that new homes are fairly tightly sealed, and actually need a certain amount of fresh air to be brought in through a heat exchanger. Even in my old, leaky, house, while it takes about 2.5 tons to effectively control the sensible heat load, it only takes about 0.5 tons of latent heat removal to maintain the dew point around 55F, even when outdoor temperatures are almost 100F.

I know this because one summer I had to use a 6000btu window unit as the main home air conditioner while I was installing a mini-split. While the indoor temperature was around 90F, the dew point was about 55F, even though the outdoor dew point was in the low 70's. Although it was hot inside, it was a dry heat, and I was comfortable with a fan blowing on me. I did drink a lot more water than usual though. Technically you could keep the house warm and dry, and just spot cool with a small personal evaporative cooler on a tabletop or something.

So why didn't I keep using the window unit? I have bark scorpions. I would usually see one or two of them every week inside the house during the summer. However, once I started keeping the house at 69F, I never saw another scorpion inside ever again, not in two years. They stay outside where it is warmer. I've never seen this recommended as a way to keep them out of the house, but it seems to work. Just remember that you heard it from me first, haha!

Geothermal is one way that you can maintain your condenser at a constant temperature day and night, as the ground is a big heat-sink. These systems are very efficient, but there is a large up-front cost to drill the hole in the ground. If you live next to a river or have a swimming pool, it is also possible to use these as heat sinks.

I am installing grid-tied solar panels soon. I live out in the country, so this is a DIY project. During the hottest parts of the day I should actually be producing more energy than I am using, and would be exporting energy to the grid. That will offset the increased air conditioning demand during the day.

wg48temp9 - 25-7-2019 at 19:37

Quote: Originally posted by Pyro_cat  


"Four Instant Ice Packs provide you with the same chilling power as 10-20 pounds of ice." https://icemakergeeks.com/do-instant-ice-packs-work-an-item-...

If the above is true then a few hundred instant cold packs are equivalent to a one ton air conditioner.


I don't know what the weight of AN in the instant ice packs above are. I estimate it would be about 1/2 lbs. So if four such packs have the same cooling capacity as 10 t0 20 lb of ice that would make the heat of solution per g of of AN five to ten times the heat of fusion of water.

i thought the heat of fusion for water was one of the highest so I was surprised that just dissolving a salt in water would be so much higher.

So I checked, assuming I did my sums correctly the heat of solution per g of AN is about twice that of the heat of fusion per g of water. So it is high but not 5 to 10 times greater than melting ice.

The definition of ton in connection with AC systems is how many tons of ice an AC system can freeze in 24 hours. So assuming American tons (1 ton = 2,000 lb) 1,000 lb of AN would have the same cooling capacity as a one ton AC unit. That's 2,000 1/2 lbs instant ice packs. That's a lot more than a few hundred. I checked, many instant ice packs are only about 1/4 lb so 4,000 of those packs would be required.

I was unable to check the ref provided as it would not load.

Pyro_cat - 28-7-2019 at 08:55

Quote: Originally posted by wg48temp9  
Quote: Originally posted by Pyro_cat  


"Four Instant Ice Packs provide you with the same chilling power as 10-20 pounds of ice." https://icemakergeeks.com/do-instant-ice-packs-work-an-item-...

If the above is true then a few hundred instant cold packs are equivalent to a one ton air conditioner.


I don't know what the weight of AN in the instant ice packs above are. I estimate it would be about 1/2 lbs. So if four such packs have the same cooling capacity as 10 t0 20 lb of ice that would make the heat of solution per g of of AN five to ten times the heat of fusion of water.

i thought the heat of fusion for water was one of the highest so I was surprised that just dissolving a salt in water would be so much higher.

So I checked, assuming I did my sums correctly the heat of solution per g of AN is about twice that of the heat of fusion per g of water. So it is high but not 5 to 10 times greater than melting ice.

The definition of ton in connection with AC systems is how many tons of ice an AC system can freeze in 24 hours. So assuming American tons (1 ton = 2,000 lb) 1,000 lb of AN would have the same cooling capacity as a one ton AC unit. That's 2,000 1/2 lbs instant ice packs. That's a lot more than a few hundred. I checked, many instant ice packs are only about 1/4 lb so 4,000 of those packs would be required.

I was unable to check the ref provided as it would not load.



I thought that was not right, the cold pack itself doesn't even freeze. 1000lbs of AN, that will never go over.

Time for a new direction.

In northern climates just make ice in the winter and save it for summer.

Water is 8lbs a gallon 2000 / 8 = 250 gallons for one ton of cooling.

25,000 gallons for 100 days @ 1 ton

https://www.swimmingpool.com/testing-water/pool-volume-calcu...


Making ice in winter is easy.

To cover several ski trails with manmade snow, you need a lot of water. According to SMI Snow Makers, it takes about 75,000 gallons (285,000 liters) of water to create a 6-inch blanket of snow covering a 200x200-foot area (61x61 meters). The system in a good-sized ski slope can convert 5,000 to 10,000 gallons (18,927 to 37,854 liters) of water to snow every minute!


A big cooler is needed. How many gallons fit in a 40 foot shipping container ?

40 foot shipping container dimensions will have some variations because they are manufactured in different ways. However, the industry standard is 40′ 0″ x 8′ 0″ x 8′ 6″ (L x W x H). In the metric system this is 12.192 m x 2.438 m x 2.591 m.

20345.6 gallons

Shipping container cost $1500 to $2500

Next up insulation !

I already played around years ago and made a few feet of ice by putting a pulsating sprinkler outside @ 5 degrees Fahrenheit and made several feet of ice on the ground in the shaded north side of the house years ago. That was still there a month after all the snow had melted.


I started a new topic Making ice in winter to cool the house in summer here https://www.sciencemadness.org/whisper/viewthread.php?tid=15...


Cooling with chemistry and chemical reactions should continue here. What can we come up with to beat traditional methods ?

So it would take 1000 lbs of AN to replicate a one ton AC unit. Yikes ! Any other material that can be used that readily available ?








[Edited on 28-7-2019 by Pyro_cat]

rockyit98 - 28-7-2019 at 10:49

Tech Ingredients explain the design and principles behind desiccant based air conditioning. This extremely efficient, DIY air conditioner is inexpensive to build and costs less than one half as much to run as a conventional, compressor based air conditioner.over 1M views!

(https://www.youtube.com/watch?v=R_g4nT4a28U)